1. Field of the Invention
The present invention relates to a frequency-characteristic-acquisition device and a method used therefor, where the frequency-characteristic-acquisition device acquires information about the frequency characteristic of a sound signal that is output from a speaker and that is transmitted to a microphone on the basis of a result of collecting a test signal by using the microphone. The present invention further relates to a sound-signal-processing device having the function of acquiring the frequency-characteristic information.
2. Description of the Related Art
Hitherto, in audio systems or the like reproducing and/or outputting an audio signal, a test signal such as a time-stretched-pulse (TSP) signal or the like is output from a speaker and collected by using a separately provided microphone. Further, information about the frequency characteristic of a sound signal output from the audio system is acquired on the basis of a result of collecting the test signal by using the microphone, and the frequency characteristic is analyzed.
More specifically, the TSP signal that is output from the speaker and collected by the microphone is subjected to Fourier-transform processing such as fast-Fourier-transform (FFT) processing, and the frequency-characteristic information is acquired. Then, a gain characteristic, a phase characteristic, and so forth are calculated on the basis of a result of the frequency-characteristic acquisition.
In the past, the frequency-characteristic information was acquired according to the following method. Namely, the sampling rate (an operation frequency) of a reproduction device which reproduces and/or outputs the TSP signal is determined to be Fs, and the number of samples subjected to the FFT processing (the number of samples of the TSP signal) is determined to be n. The TSP signal includes signals generated in the range of from 0 to Fs/2 Hz, where gains of the signals generated at each of intervals of Fs/n Hz are the same as one another.
For example, where the sampling rate is shown by the equation Fs=44.1 kHz and the sample number n is shown by the equation n=4096, the TSP signal includes signals generated in the frequency range of from 0 to 22.05 (44.12) kHz, where gains of the signals generated at each of intervals of about 10.8 (44100/4096) Hz are the same as one another.
When the above-described TSP signal is obtained, for example, it becomes possible to analyze the frequency characteristic of each of frequency bands included in the range of from 0 to 22.05 kHz at intervals of about 10.8 Hz.
Known technologies relating to the present invention are disclosed in Japanese Unexamined Patent Application Publication No. 2000-097763 and Japanese Unexamined patent Application Publication No. 04-295727, for example.